Northern Ireland's police chief George Hamilton said: "We believe violent dissident republican groups are behind this, they will use whatever excuse they can to bring about unrest and to have young people involve themselves in violence against the police.

"We believe there are members of a variety of dissident groupings in this disorder – the so-called New IRA is probably the primary grouping behind this disorder and behind these threats to police and these murderous attacks on police.

"If this continues, it's only a matter of time before a police officer or a child or young person involved in this violence gets very seriously injured or worse."

Image: Catholic bishop of Derry Donal McKeown speaking at a rally on Fahan street, in protest against the ongoing violence and disorder

It is understood some of those involved in the violence are not even in their teenage years.

On Friday, hundreds of people attended a community rally in Derry, demonstrating their opposition to the violence.

The Bishop of Derry told those in attendance the city would not be drawn back into years of suffering and loss.

The area remained quiet on Friday evening, with no signs of fresh disorder by 11pm.

Image: A rioter threw a petrol bomb at a van from close range in Derry

Police Land Rovers were engulfed in flames in the Republican neighbourhood as a crowd of about 200 people caused disorder on Thursday night.

Many of those involved were youths, with some said to have been of a very young age.

A hooded rioter was seen hurling a petrol bomb at the windscreen of a passing van from point-blank range.

Image: Orange Order parades were held across Northern Ireland to commemorate the Battle of the Boyne in 1690

Thousands of Orange Order members took part in the Twelfth of July parades across Northern Ireland amid sporadic violence.

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They have passed off peacefully in recent years – helped largely by the resolution of a long-standing parading flashpoint dispute in Belfast.

Mr Adams was leader of Sinn Fein from 1983 until February 2018, while Mr Storey has been the party's northern chairman.